It has been recognized that it is desirable to be able to monitor a variety of different types of gas concentrations in the ambient atmosphere in a given region. Examples include environmental monitoring such as detecting toxic or otherwise dangerous gases that can result from spills or leaks, or, monitoring gases in a variety of industrial process settings such as beverage manufacture, food manufacture and the like. Sensors of human generated odors or vapors or, exhaled breath have been used for medical diagnosis or analysis. Interest in other types of chemical gas monitoring grows out of wanting to detect dangerous circumstances such as leakage of combustible or explosive gases as might be released in a fire, or, explosion as well as gases expelled from various kinds of explosives such as land mines and the like.
Known systems for monitoring on-going processes often compare current process signatures to a signature associated with an optionally functioning process. Such comparisons are effective and useful where what is required is to carry out the process to produce a result as close as possible to that produced by an optionally functioning process. However, not all monitoring corresponds to this model.
Particularly in circumstances of potential danger such as when dealing with combustible or explosive gases, as well as explosive materials themselves, it would be desirable to have available compact and light weight detectors which could be easily carried or worn by personnel in the region of interest. Such detectors preferably would be battery powered with extended lifetimes due to relatively low power requirements of the detector. Additionally, it would be preferable if such detectors could provide readings with a relatively high degree of reliability so as to minimize false positives while at the same time reliability indicating the presence of dangerous levels of the relevant gas.